 @media only screen and (max-width: 1960px){
   html,
   body {
     font-size: 73.5px;
   }
 }
 /* for 1600px width screen */
 @media only screen and (max-width: 1600px){
   html,
   body {
     font-size: 60px;
   }
 }
 /* for 1440 px width screen */
 @media only screen and (max-width: 1440px){
   html,
   body {
     font-size: 54px;
   }
 }
 /* for 1280 px width screen */
 @media only screen and (max-width: 1280px){
   html,
   body {
     font-size: 48px;
   }
 }
 /* for 1080 px width screen */
 @media only screen and (max-width: 1080px){
   html,
   body {
     font-size: 40.5px;
   }
 }
 /* for 1024 px width screen ipad pro*/
@media only screen and (max-width: 1024px){
  html,
  body {
    font-size: 38.4px;
  }
}
 /* for 960 px width screen */
 @media only screen and (max-width: 960px){
   html,
   body {
     font-size: 36px;
   }
 }
 /* for 800 px width screen */
 @media only screen and (max-width: 800px){
   html,
   body {
     font-size: 30px;
   }
 }
 /* for 768px width screen ipad 小米mix3*/
 @media only screen and (max-width: 786px){
   html,
   body {
     font-size: 29.475px;
   }
 }
 /* for 720 px width screen 小米6*/
 @media only screen and (max-width: 720px){
   html,
   body {
     font-size: 27px;
   }
 }
 /* for 640 px width screen */
 @media only screen and (max-width: 640px){
   html,
   body {
     font-size: 24px;
   }
 }
 /* for 600 px width screen */
 @media only screen and (max-width: 600px){
   html,
   body {
     font-size: 22.5px;
   }
 }
  /* for 562.5 px width screen iphonex */
 @media only screen and (max-width: 562.5px){
   html,
   body {
     font-size: 21.09375px;
   }
 }
 /* for 540 px width screen */
 @media only screen and (max-width: 540px){
   html,
   body {
     font-size: 20.25px;
   }
 }
 /* for 480 px width screen */
 @media only screen and (max-width: 480px) {
   html,
   body {
     font-size: 18px;
   }
 }
/* for 435 px width screen  Nexus 6p */
 @media only screen and (max-width: 435px){
   html,
   body {
     font-size: 16.3125px;
   }
 }
/* for 414 px width screen  iphone6plus 7plus*/
 @media only screen and (max-width: 414px){
   html,
   body {
     font-size: 15.525px;
   }
 }
/* for 411 px width screen Nexus 5x*/
 @media only screen and (max-width: 412px) {
   html,
   body {
     font-size: 15.4125px;
   }
 }
 /* for 400 px width screen */
 @media only screen and (max-width: 400px) {
   html,
   body {
     font-size: 15px;
   }
 }
 /* for 393 px width screen 小米mix3*/
 @media only screen and (max-width: 393px) {
   html,
   body {
     font-size: 14.7375px;
   }
 }
 /* for 384 px width screen */
 @media only screen and (max-width: 384px){
   html,
   body {
     font-size: 14.4px;
   }
 }
 /* for 375 px width screen iphone6 7*/
 @media only screen and (max-width: 375px){
   html,
   body {
     font-size: 14.0625px;
   }
 }
 /* for 360 px width screen */
 @media only screen and (max-width: 360px){
   html,
   body {
     font-size: 13.5px;
   }
 }
/* 360/320*12 */
 /* for 320 px width screen iphone4 5*/
 @media only screen and (max-width: 320px){
   html,
   body {
     font-size: 12px;
   }
 }
/* for double screen width Retina screen */